1. Field of the Invention
Magnetron sputtering of material from a target onto a substrate.
2. Brief Description of the Prior Art
Sputtering is a thin film coating process using a plasma discharge in a sputtering gas to produce ion bombardment of a target of the material to be coated onto a substrate. Because of the ion bombardment, neutral atoms of the target material are ejected from the target surface toward the substrate and form a thin film coating. Magnetic fields have been used in sputtering devices for a variety of reasons. For example, U.S. Pat. No. 4,046,660, issued Sep. 6, 1977 discloses use of a magnetic field of a particular geometry to permit plasma operation at lower gas pressures, and magnetic control of the plasma to control the charged particle flux on the substrate. A class of sputtering devices has been developed that use an array of magnets to increase sputtering efficiency by confining the plasma to the vicinity of the target. The magnets are rotated concentrically with the target in an attempt to even out the erosion of the target. However, as sputtering progresses, a groove forms in the target and deepens, shortening target life, changing the distribution of sputtered material on the substrate, and permitting redeposition of target material as particulates on the target outside of the groove.